Best Image Optimisation Plugins for WordPress
Image optimisation is three jobs sold as one, and buying the wrong one is why people optimise their library and see no improvement. Compression reduces file size at the same dimensions. Resizing stops you serving a 4000px photograph into an 800px slot. Format conversion replaces JPEG and PNG with WebP or AVIF, which are simply better at the same visual quality.
Resizing is usually the largest win and the one nobody buys a plugin for, because a correctly sized image beats a heavily compressed oversized one every time. Format conversion is the 2026 differentiator, since AVIF support is now common enough to expect. This article covers all three and what each vendor charges for them.
Verified August 2026. Prices confirmed against vendor pages.
WebP, AVIF, and what the formats buy you
WebP is universally supported now and typically produces meaningfully smaller files than JPEG at equivalent quality. If you are still serving JPEGs everywhere, converting is the single largest payload reduction available to most sites and it requires no visual compromise.
AVIF goes further, producing smaller files again, particularly on photographic content and on images with gradients where JPEG artefacts are most visible. Its costs are real: encoding is slower and more computationally expensive, which matters if you process images on your own server, and support, while now broad, is not quite universal. The sensible arrangement is to serve AVIF where the browser accepts it, WebP where it does not, and the original as a final fallback, which every capable plugin here handles automatically.
The decision that actually shapes your bill is local processing versus cloud. Local plugins use your server’s resources and are free or nearly so, but bulk-converting ten thousand images will make the site slow while it runs, and AVIF encoding on shared hosting can be painfully slow. Cloud services do the work elsewhere and charge by volume, which is faster and turns optimisation into a recurring cost.
The 6 options compared
1. ShortPixel
The best pricing structure in the category because it offers something almost nobody else does: one-time credits that never expire. Ten thousand credits from $9.99, or 50,000 for $29.99, bought once and used whenever.
That model fits how most sites actually work. You have a library of existing images to convert, which is a one-off task, and then you add a handful of images a month, which is a trickle. Paying a subscription forever for a trickle is the wrong shape; buying 50,000 credits once for $29.99 is the right one. There is a free plan at 100 credits a month for evaluation, and an unlimited subscription at $9.99 a month including 500GB of CDN traffic if your volume genuinely justifies it. WebP and AVIF conversion are supported, with lossy, glossy and lossless compression options.
- Price: Free 100 credits/mo; 10,000 from $9.99 one-off; $9.99/mo unlimited
- Formats: WebP and AVIF
- Best for: Most sites, thanks to non-expiring one-time credits
- Watch out for: Credits are consumed per image and per thumbnail size
2. Imagify
From the WP Rocket team, and priced by data volume rather than image count, which suits sites with many small images. The free Starter plan allows 20MB a month, roughly 200 images, with a 2MB per-image limit and unlimited websites.
Growth is $5.99 a month, or $4.99 billed annually, for 500MB a month, about 5,000 images, with unlimited upload size and additional storage at $5 per GB. Infinite is $11.99 a month, or $9.99 annually, for unlimited optimisation with no extra costs. The detail worth noting is that every plan covers unlimited websites, which makes the $9.99 Infinite plan unusually good value for an agency: unlimited images across unlimited client sites for around $120 a year. WebP and AVIF conversion are included on all plans, including free.
- Price: Free 20MB/mo; Growth $4.99/mo; Infinite $9.99/mo annually
- Formats: WebP and AVIF on every plan
- Best for: Agencies, since all plans cover unlimited sites
- Watch out for: Free tier caps images at 2MB each
3. EWWW Image Optimizer
The option that can run entirely on your own server, processing images locally with no per-image cost and no external service involved. For a site with a large existing library and a tight budget, that is a genuinely different proposition.
Local processing means no credits, no monthly allowance, and no third-party service receiving your media. It also means your server does the work, which on shared hosting is slow, and AVIF encoding in particular is demanding enough that a bulk conversion of several thousand images is an overnight job rather than a coffee break. A paid cloud tier exists for people who want the work done elsewhere. Choose it when you have server capacity or when keeping images off external services matters to you.
- Price: Free local processing; paid cloud tiers available
- Formats: WebP and AVIF, encoded locally
- Best for: Large libraries, tight budgets, capable servers
- Watch out for: Bulk AVIF encoding is slow on shared hosting
4. Optimole
A different architecture: rather than optimising files in your media library, it serves images through its own CDN, resizing and converting them on the fly for each visitor’s device and connection.
The advantage is that your originals are never touched, so there is no risky bulk conversion and nothing to undo if you change your mind. It also solves the resizing problem properly, since the image delivered is sized for the actual viewport rather than for a fixed set of thumbnails generated at upload. The trade is dependency: your images are served by a third party, and if the service is unavailable or you stop paying, your image delivery is affected in a way that a plugin writing WebP files into your uploads folder is not. Check the free tier’s limits against your traffic before assuming it fits.
- Price: Free tier with limits; paid plans by volume
- Formats: Converted on the fly per browser
- Best for: Sites wanting per-device sizing without touching originals
- Watch out for: Image delivery depends on the service continuing
5. Converter for Media
A free plugin doing one job well: converting your existing library to WebP and AVIF and serving the converted versions automatically, without an account or a credit system.
If format conversion is specifically what you need, and compression and resizing are already handled or not your bottleneck, this is a clean answer at no cost. It keeps the originals and serves the modern format when the browser supports it, which is the correct behaviour and also means the change is reversible. As with any local processing, bulk conversion of a large library takes time and server resources, so run it when the site is quiet. It pairs well with the free approach below rather than competing with the paid services above.
- Price: Free
- Formats: WebP and AVIF, with originals retained
- Best for: Format conversion alone, without a subscription
- Watch out for: Does not address compression or resizing
6. Resizing before you upload
Free, requires no plugin, and produces a larger improvement than compression on most sites. A photograph straight from a phone is several thousand pixels wide and several megabytes; the slot it occupies on your page is perhaps 800 pixels.
Compressing that original by 60% still leaves an image four times larger than necessary. Resizing it to the width it will actually display eliminates the excess entirely, and then compression works on a sensible starting point. Set WordPress’s large image threshold appropriately, decide the maximum width your layout ever uses, and resize to that before uploading. The habit costs nothing per image and it means your media library stops growing at a rate your hosting will eventually charge you for. It also makes every subsequent optimisation faster and cheaper, since credits and allowances are consumed by the number and size of what you process.
- Price: Free
- Formats: Not applicable; this is about dimensions
- Best for: Everyone, and it is usually the biggest single win
- Watch out for: Needs to become a habit, not a one-off cleanup
Comparison table
| Option | Price | Meter | AVIF | Processing |
|---|---|---|---|---|
| ShortPixel | Free 100/mo; $9.99 one-off | Credits, non-expiring | Yes | Cloud |
| Imagify | Free 20MB/mo; $9.99/mo unlimited | Data volume | Yes, all plans | Cloud |
| EWWW | Free local; paid cloud | None when local | Yes | Local or cloud |
| Optimole | Free tier; paid by volume | Visits and bandwidth | Yes, on the fly | Their CDN |
| Converter for Media | Free | None | Yes | Local |
| Resize before upload | Free | None | Not applicable | Your computer |
Converting an existing library without breaking it
Bulk conversion is the step where things go wrong, because it touches thousands of files at once and the damage is not always visible immediately. Six precautions.
- Back up the uploads directory first, separately. Not as part of a full site backup you would have to restore entirely, but as a copy of the folder you can put back on its own.
- Keep originals. Every plugin here can retain them. The disk space is cheap and the alternative, discovering the compression was too aggressive after the originals are gone, is not recoverable.
- Convert a hundred images first and look at them. Photographs, logos with flat colour, screenshots with text. Compression artefacts appear differently in each, and text is where they show worst.
- Run bulk conversion when the site is quiet. Local processing consumes server resources and will slow the site while it runs; cloud processing consumes credits at a rate worth watching.
- Check thumbnail counts before buying credits. WordPress generates several sizes per upload, and credit-based services usually charge for each, so a thousand images can consume five thousand credits. This is the most common budgeting surprise.
- Verify the fallback works. After conversion, load the site in a browser and confirm images appear. A misconfigured server rule that serves WebP to a browser expecting JPEG produces broken images across the whole site at once.
One more: delete the unused thumbnail sizes your theme no longer generates. Sites that have changed themes twice often carry four obsolete sizes of every image, which costs storage, costs conversion credits, and benefits nobody.
Related guides
Frequently asked questions
Should I use WebP or AVIF?
Both, with AVIF served where supported and WebP as the fallback. Every capable plugin here handles that negotiation automatically, so there is no reason to choose.
Will optimisation ruin my image quality?
Not at sensible settings. Test on a hundred images including logos and screenshots before running the whole library, because text and flat colour show artefacts long before photographs do.
How many credits will my library need?
More than your image count, because WordPress generates several thumbnail sizes per upload and most services charge per file. Check how many sizes your theme registers before buying a plan.
Is local or cloud processing better?
Local is free and slow; cloud is fast and metered. On a big library with modest hosting, cloud is worth the money once. For a trickle of new uploads, local costs nothing and you will not notice.
Do I still need lazy loading?
WordPress applies it by default to images below the fold, and it complements optimisation rather than replacing it. Make sure your above-the-fold image is not lazy loaded, since that delays your Largest Contentful Paint.
What if I change my mind after converting?
You restore the originals, which is why keeping them matters. Plugins that serve converted copies alongside the originals are reversible; ones that overwrite are not.
The verdict
Resize before uploading, first. It is free, it is usually the largest single improvement, and it makes everything you buy afterwards cheaper because you are processing fewer oversized files.
Then ShortPixel, on one-time credits. Ten thousand from $9.99 or 50,000 for $29.99, never expiring, which matches the real pattern of a one-off library conversion followed by a trickle of new uploads.
If you manage several sites: Imagify Infinite at $9.99 a month billed annually, because every plan covers unlimited websites and that makes unlimited optimisation across a portfolio cost about $120 a year.
If you want to spend nothing: EWWW processing locally, or Converter for Media if format conversion is all you need. Both are free, both are slower, and on a site adding a few images a week you will never notice the difference.
